Fluorophenoxy-pyridazines as selective herbicides

ABSTRACT

Herbicidal composition which comprises as an active ingredient of a 3-phenoxypyridazine compound having the formula WHEREIN X is hydrogen atom or chlorine atom, R1 is trifluoromethyl group or fluorine atom and R2 is hydrogen atom or chlorine atom, provided that, where X is hydrogen atom, R1 is trifluoromethyl group or fluorine atom and R2 is hydrogen atom or chlorine atom and, where X chlorine atom, R1 is trifluoromethyl group and R2 is hydrogen atom or chlorine atom and an agriculturally-acceptable carrier. Method for inhibiting the growth of undesirable plants which comprises applying to the locus to be protected a herbicidally effective amount of said 3phenoxypyridazine compound.

United States Patent Johima Mar. 28, 1972 [54]FLUOROPHENOXY-PYRIDAZINESAS SELECTIVE HERBICIDES [72] inventor: TeruomiJojima, Tokyo,.lapan [73] Assignee: Sankyo Company Limited, Tokyo, Japan[22] Filed: Feb. 24, 1969 [21] Appl. No: 801,745

[30] Foreign Application Priority Data Feb. 28, 1968 Japan ..43/ 12727[52] [1.8. CI. ..71/92, 260/250 A [51] Int. C1. 9/22 [58] Field oiSearch ..71/92; 260/250 [56] References Cited UNITED STATES PATENTS2,905,672 9/1959 Steck ..260/250 3,399,987 9/1968 Woods et al ..71/923,427,146 2/1969 Tamura ct al ..71/92 FOREIGN PATENTS OR APPLICATIONS15,716 /1966 Japan ..71/92 6,358 6/1966 Japan ..71/92 OTHER PUBLICATIONSTamura eta1., 11, Synthesis of Pyridazine Ders. etc., (1963) CA p. 2,928(1964) Tamura et al., 111, 3-Phenoxypyridazine as a New etc."; (1966)CAp. 4,563 (1966) J ojima et al., Syn. of Pyridazine Ders. etc."; CA63 p.601 (1965) Primary Examiner-Lewis Gotts Assistant Examiner-G. HollrahAttorney-McGlew and Toren ABSTRACT Herbicidal composition whichcomprises as an active ingredient of a 3-phenoxypyridazine compoundhaving the for- .mula

wherein X is hydrogen atom or chlorine atom, R, is trifluoromethyl groupor fluorineatom and R is hydrogen atom or Method for inhibiting thegrowth of undesirable plants which comprises applying to the locus to beprotected a herbicidally egttectiye amount ot: said 3-phenoxypyridazinecompound.

j 3 Claims, No Drawings FLUOROPHENOXY-PYRIDAZINES AS SELECTIVEHERBICIDES This invention relates to a new use of certain3-phenoxypyridazine compounds as a herbicide. More particularly, itrelates to a method for inhibiting the growth of undesirable plantswhich comprises applying to the locus to be protected a herbicidallyeffective amount of such 3-phenoxypyridazine compound. Also, it relatesto a herbicidal composition which comprises as an active ingredient such3-phenoxypyridazine compound and an agriculturally-acceptable carrier.Still more particularly, it is concerned with a method for inhibitingthe growth of undesirable plants, i.e., a wide variety of harmful weedswhich comprises applying to the locus to be protected, in a herbicidallyeffective amount, a 3-phenoxypyridazine compound having the formulawherein X is hydrogen atom or chlorine atom, R is trifluoromethyl groupor fluorine atom and R is hydrogen atom or chlorine atom, provided that,where X is hydrogen atom, R is trifluoromethyl group or fluorine atomand R is hydrogen atom or chlorine atom and where X is chlorine atom, Ris trifluoromethyl group and R, is hydrogen atom or chlorine atom. It isalso concerned with a herbicidal composition which comprises as anactive ingredient such a 3-phenoxypyridazine compounds (I) as specifiedhereinabove, together with an agriculturally-acceptable carrier.

Herbicidal activity of some 3-phenoxypyridazine compounds was reportedin the art. Thus, it was disclosed in Agricultural and BiologicalChemistry, 27, 728 (1963) and ibid, 29, 157 (1965) that some6-chloro-3-alkyl(chloro, alkoxy or nitro)substituted phenoxypyridazinecompounds show herbicidal activities. It was also shown in Agriculturaland Biological Chemistry, 30, 423, (1966) that S-phenoxypyridazine showsa desirable herbicidal activity in a submerged pot test. Also, it wasfound that the 3-phenoxypyridazine having the formula wherein Xrepresents hydrogen atom, methyl group or chlorine atom and n is aninteger of l to inclusive; each X may be the same or different and, whenn is an integer of 4 or 5, each X represents chlorine atom as well assome acid addition salts thereof show potent herbicidal activities on awide variety of weeds, especially grasses and perennial weeds(Netherlands Pat. application No. 660,4248, filed by Sankyo CompanyLimited, Japan and laid open to public inspection on Aug. 26, 1966).

As a result of further extensive investigations on herbicidal activityof numerous 3-phenoxypyridazine compounds, it has now been found that aspecific group of the 3-phenoxypyridazine compounds having the formula(I) show similar herbicidal effects on such undesirable plants as, forexample, grasses and perennial weeds and especially they show potentherbicidal effects on the broad-leafed weeds without any degree ofphytotoxicity and also that they show favorable selective herbicidaleffects on beneficial plants, for example, stone-leek, carrot, spinachand the like, as compared with such known 3-phenoxypyridazine compounds.

It is, accordingly, a primary object of this invention to provide anovel and effective method for inhibiting growth of undesirable plantssuch as grasses, perennial and broad-leafed weeds and so on whichcomprises applying to the locus to be protected at herbicidallyeffective amount of the 3-phenoxypyridazine compound (I) as specifiedabove. It is another object of this invention to provide a herbicidalcomposition which comprises as an active ingredient the above-specified3- phenoxypyridazine compounds (I) and an agriculturally-acceptablecarrier, if desired together with a suitable adjuvant. Other objects ofthis invention will become apparent to those skilled in the art withreference to the detailed description of the invention.

The 3-phenoxypyridazine compounds (I) which may be employed as an activeingredient in this invention are new compounds which were not disclosedin prior art literatures.

These 3-phenoxypyridazine compounds which may be employed as an activeingredient in this invention can be easily prepared by any of thefollowing procedures; (a) by melting 3- chloropyridazine together withthe corresponding substituted phenol in the presence of a base or (b) bycatalytic reduction of the corresponding 3-substituted phenoxy-6-chloropyridazine.

More particularly, the former procedure (a) may be preferably carriedout by melting 3-chloropyridazine together with a substituted phenol anda base such as anhydrous potassium or sodium carbonate in the absence ofa solvent. In this procedure, the melting temperature is preferably inthe range of about l00180 C., the higher temperature being sometimesundesirable because of possible decomposition of a starting3-chloropyridazine. The reaction is usually effected in about 5-15minutes.

The latter procedure (b) may be preferably carried out by any of variousprocedure for catalytic reduction well-known in the art, most preferablyby employing Raney nickel or palladium on carbon. The reduction may begenerally conducted at normal temperature and under pressure or underatmospheric pressure, suitably with heating to about 40-50 C., in thepresence of a solvent such as an organic solvent, for example, a loweralcohol, benzene, toluene, 2-methoxyethanol, glacial acetic acid orethyl acetate, a mixture of water and any of these organic solvents, butpreferably in the presence of a lower alcohol, for example, methanolbecause of the solubility of a starting material therein as well aseasiness of handling. In both procedures, the final product may berecovered by a known technique.

Representative examples of the 3-phenoxypyridazine compounds having theformula (I) are given hereinbelow only for the purpose of illustration:

1. 3-(2-fluorophenoxy)pyridazine (m.p. 5758 C.);

2. 3-(3-fluorophenoxy)pyridazine (m.p. 63-65 C.);

3. 3-(4-fluorophenoxy)pyridazine (m.p. 87-89 C.);

4. 3-(2-chloro-4-fluorophenoxy)pyridazine (m.p. 1l4-l 16 5.3-(Z-trifluoromethylphenoxy)pyridazine (m.p. 67-68 6.3-(2-trifluoromethylphenoxy)-6-chloropyridazine (b.p. l38-l43 C./0.85mm. Hg);

7. 3-(3-trifluoromethylphenoxy)pyridazine (m.p. 50-51 8.3-(3-trifluoromethylphenoxy)-6-chloropyridazine (m.p. 63-65 C.);

9. 3-(2-chloro-5-trifluoromethylphenoxy)pyridazine (m.p. 76 C.

l0. 3-(2-chloro-5-trifluoromethylphenoxy)-6- chloropyridazine (m.p. 106C.);

11. 3-( 3-trifluoromethyl-4-chlorophenoxy)pyridazine (m.p. 9798 C. and

12. 3-(3-trifluoromethyl-4-chlorophenoxy)-6- chloropyridazine p(m.p.78-79 C.).

The active compounds (I) in this invention can be applied in any ofvarious types of the compositions commonly employed in the art. Ingeneral, the active compouns can be diluted or extended with anagriculturally-acceptable carrier commonly employed in the art such asinert solids, water and organic liquids.

The active compounds (I) will be included in such compositions insufficient amount so that they can exert a herbicidal effect. Usuallyfrom about 0.5-95 percent by weight of the active compounds may beincorporated into such formulations.

Solid compositions can be in the fonn of powders or dusts. Concentratedsolid compositions, if desired, may be prepared and diluted with inertsolids to form-dusts prior to application. Natural clays, higherabsorptive such as attapulgite or relatively non-absorptive such aschina clays, diatomaceous earth, bentonite, synthetic fine silica,calcium silicate, talc, pyrophyllite, and otheragriculturally-acceptable solid carriers conventionally employed inpowder herbicidal compositions can be satisfactorily used. The activecompound usually makes up from about 0.5-90 percent, preferably fromabout 2-10 percent of these powder compositions. The solids ordinarilyshould be very finely divided.

Liquid compositions including the active compound (I) can be prepared byadmixing the active compound with a suitable liquid diluent medium,together with a suitable emulsifying agent. Typical of the liquid mediacommonly employedare methanol, benzene, toluene and the like. The activeingredient usually makes up from about 05-50 percent of these liquidcompositions. Some of these compositions are designated to be used assuch, and others to be diluted or extended with large quantities of asuitable liquid medium such as water.

Compositions in the form of wettable powders can include one, or moresurface active agents, such as wetting or dispersing agents. The surfaceactive agents cause the compositions of wettable powders to disperseeasily in water to give aqueous sprays. The active ingredient usuallymakes up from about 50-80 percent of the compositions. The surfaceactive agents employed can be of the anionic, cationic or nonionictypes. They include, for example, sodium long-chain carboxylates,alkylaryl sulfonates, sodium lauryl sulfate, polyethylene oxides, ligninsulfonates and other surface active agents commonly employed in the art.

When used as a pre-emergence treatment, it will be desirable to includea fertilizer, an insecticide, a fungicide or other herbicide such as2,4-dichlorophenoxyacetic acid, Z-methyl- 4-chlorophenoxyacetic acid andsalts, amides and esters thereof, as well as sodiumpentachlorophenoxide, 2,4- dichlrophenyl-4'-nitrophenyl ether,3-methylphenyl-4- nitrophenyl ether, 2,4,6-trichlorophenyl-4-nitrophenylether, 2-methylthio-4,6-bis(ethylamino)-1,3,5-triazine and the like.

in order to illustrate the preparation of the herbicidal composition inthis invention, the following examples are given. it is, of course, tobe understood that this invention is not limited thereto. All parts aregiven by weight unless otherwise stated.

EXAMPLE 1 Fifty parts of 3-(2-fluorophenoxy)pyridazine, 45 parts ofbentonite and parts of polyoxyethylene alkyl aryl ether were mixed andpulverized to give a wettable powder.

EXAMPLE 2 A mixture of parts of 3-( 3-fluorophenoxy)pyridazine, 50 partsof bentonite, 40 parts of talc and a small amount of sodium alkylbenzenesulfonate was mixed up with water to make granules, which were thendried and screened to give a granule having a particle size in the rangeof -80 mesh.

EXAMPLE 3 Fifty parts of 3-(4-fluorophenoxy)pyridazine, 45 parts ofbentonite and 5 parts of sodium alkyl benzene sulfonate werehomogeneously mixed to give a wettable powder.

EXAMPLE 4 Five parts of 3-(3-trifluoromethylphenoxy)pyridazine, 50 partsof bentonite, 38 parts of talc and 7 parts of sodium alkylbenzenesulfonate were uniformly mixed up with water to make granules, whichwere then dried and screened to give a granule having a particle size inthe range of 20-80 mesh.

The herbicidal method of this invention comprises applying theabove-specified active compounds to the locus or area to be protectedfrom undesirable plant growth. The active compound is, of course,applied in an amount sufiicient to exert the desired herbicidal action,usually in such an amount sufficient to provide about 50-300 g. of theactive compound per 10 ares.

it may be desirable to apply the active compound, in the form of theaforesaid composition, directly to the soil prior to weed infection,which is known as a pre-emergence treatment.

The herbicidal effects of the active compounds in this invention aremore fully illustrated by the following experiments.

EXPERIMENT l Pre-emergence Treatment Test Seeds of the following weeds,i.e., bamyardgrass, Taisai (Brassica chinensis L.) and common chickweed, each being 50 seeds, were sowed in a ground plot of 1 squaremeter, in admixture with the surface soil in the depth of about 2 cm.thereunder. The test compounds as indicated hereinbelow were formulatedinto wettable powders by a conventional procedure. Those wettablepowders were diluted with water and applied by spraying to the seededground at rates of 12 g./ are and 40 g./ are of the test compound. Theplot was placed in a greenhouse. On the 25th day after application,germination-inhibiting or killing rates for the test compound werevisually investigated. The results are summarized in the following Table1.

TABLE I [Killing rates of S-phenoxypyridazine compounds against grassesand broad-leafed weeds] Killing rate percent Common Weed BarnyardgrassTaisai chick weed Application rate (gJare) 12 40 12 40 12 40 Testcompound:

1 100 100 100 100 100 100 80 80 80 90 90 70 80 80 95 95 80 90 90 1 100 v100 s 100 u 100 a 100 I! 100 B 100 100 B 90 100 6 85 85 100 e 100 v 100100 s 100 85 100 6 100 v 100 a 100 n 100 v 100 v 12 85 85 100 s3-phenoxypyrldazinenn 40 7O 50 60 3-(2-methylphenoxy)- 1 pyridazine 90100 50 70 55 60 3-(2,5dimethylphenoxy)pyrldazine 90 100 60 80 70 903-(3-methyl-4-iso ropylphenoxy)pyri azine. 20 30 0 70 20 403-(3-methyl-4-secbutylphenoxy)- pyridazine 40 100 20 70 30 50 Non-treated 5 3 i0 Test eompoundis indicated by means of the number asgiven to the phenoxypyridazine compounds listed hereinabove.

Nora-The symbol (0) marked right-upwardly to the number means that allof the weeds were killed due to severe chiorosis.

EXPERIMENT 2 i-ierbicidai Test in Paddy Field Soils for paddy field werecharged into a pot of a surface area of square centimeters, anappreciate number of rice plants (at four or five leaf stage) andslender spikerush were 5 transplanted, seeds of barnyard grass v ve resowed and then water was filled at a depth of about 3 cm. over the soilsurface. On the next day, the wettable powders containing the testcompounds shown below and formulated as in the above Experiment 1, werediluted with water and applied by spraying to the soil at a rate givenbelow of the specific compound per are. After 30 days of theapplication, the growth of slender spikerush, barnyard grass andspontaneously growing broadleafed weeds as well as that of rice plantswere visually observed. The results are summarized in the followingTable II. In this table, herbicidal activities of the test compoundsagainst bamyardgrass and broad-leafed weeds were evaluated upon thefollowing grades;

Herbicidal rating 4:ll-20% (-ditto-) 3121-40 70 (-ditto-) 2:41-60%(-ditto-) 1:6l80% (-ditto-) man-100% (-ditto-) And, herbicidalactivities of the test compound against slender spikerush were evaluatedupon the grade as defined hereinbelow.

2H2- em 1- phenoxy pyrldazlne il-(2A-dimethyl- 3(3-methyl-4-lsoproplphenoxy)- pyrl azine .Not observed.

' See footnote at end of Table I.

EXPERIMENT 3 Susceptibility test of 3-phenoxypyridazine compounds tobeneficial plants Following the same test procedure and condition asdescribed in the above Experiment l and the same herbicidal ratings asreferred to barnyardgrass and broad-leafed weeds in the above Experiment2 except that rates of the active com- 5 Idead pound per are were 25.0g., 12.5 g. and 6.25 g., as a host plant 4 I severely damag wereemployed stone-leek, carrot and spinach, and as a weed 3 rcons derablyda g seed was employed large crabgrass, susceptibility of those 3- 2moderately damaged 30 phenoxypyridazine compounds as specified below wasinl slightly damaged vestigated to such beneficial plants. 0 not damagedThe results are summarized in the following Table III.

TABLE III Killing rate Host plant or weed Stone-leek Carrot SpinachLarge crabgrass Rate (gJare) 25.0 12.5 6.25 25.0 12. 5 6. 25 25. o 12. 56. 25 25.0 12. 5 6. 25

Test compound:

1 3 1 0 5 2 0 4 3' 0 5 5 5 3 3-4 0 0 0 0 0 3-4 0 0 4 4 3 4 2 0 0 2 0 0 31 1 4 4 3 Control: 3-(2-rnethylphenoxy)- pyridazine 2 2 4 4 4 3 3 3 5 55 See footnote at end of Table I.

TABLE ll Ma Herbicidal activity of 3-phenoxypyridazine compound againstbroad-leafed weeds and pe en ni weeds Herbicidal activity Slenderspikerush Broadleafed weed Barnyardgrass Test compound S-phenoxysvzinsfi fiuorophenoxy)-pyridazine.

It will be noted from the above results that the 3-phenoxypyridazinecompounds in this invention do not exert any unfavourable degree ofkilling effect on beneficial plants, as compared with the control3-phenoxypyridazine, and on the other hand, they show a considerabledegree of herbicidal activity against large crabgrass harmful weed.

What is claimed is:

l. A method for inhibiting the growth of undesirable plants in thepresence of stone leek which comprises applying to the locus thereof aherbicidally effective amount of 3-(2- fluorophenoxy)-pyridazine.

2. A method for inhibiting the growth of undesirable plants in thepresence of carrots which comprises applying to the locus thereof aherbicidally effective amount of 3-(2- fluorophenoxy)-pyridazine.

3. A method for inhibiting the growth of undesirable plants in thepresence of spinach which comprises applying to the locus thereof aherbicidally effective amount of 3-( 2-

2. A method for inhibiting the growth of undesirable plants in thepresence of carrots which comprises applying to the locus thereof aherbicidally effective amount of 3-(2-fluorophenoxy)-pyridazine.
 3. Amethod for inhibiting the growth of undesirable plants in the presenceof spinach which comprises applying to the locus thereof a herbicidallyeffective amount of 3-(2-fluorophenoxy)-pyridazine.